This is so tedious, I don't know why your anser begins with "just". Please make it easier to do by including a remove from playsit option on the menu next to the currently playing track. Apple has had this feature for a long time.
Re: How do I delete a song from a playlist while on my iPhone?
This solution only works when you have only a few songs in a playlist. If you have a playlist with a couple of hundred songs, this solution is simply not achievable, because I can’t find that specific song in such a big playlist.